I. Field of the Invention
The present invention is related to tissue surveillance systems.
II. Discussion of the Prior Art
Systems and methods exist for determining when a probe, needle, catheter or other devices make contact with a particular tissue, e.g. U.S. Pat. No. 5,836,990 to Li entitled “Method and Apparatus for Determining Electrode/Tissue Contact.” The Li patent teaches a method for determining when a catheter makes contact with tissue covered with an ionic liquid. The system measures the electrical impedance at a distal end of the catheter and determines tissue contact has been made when the impedance increases. The system does not identify the type of tissue contacted and presumes the tissue is covered in an ionic liquid. Accordingly, a need exists for a system and method that identifies tissue and uses this information in medical procedures.
Systems and methods also exist for controlling the level of ablation of tissue. These systems monitor the impedance of tissue being ablated to determine if the ablation energy is optimal. The systems generally measure impedance to within approximately 20 ohms. These systems do not determine when sufficient therapy has been applied to the tissue or employ impedance measurement with low tolerance levels. Accordingly, a need exists for a system that may control any form of therapy by monitoring characteristics of an electrical signal applied to the tissue.